This invention relates, in general, to a method and apparatus for treating material at relatively high temperatures, and in particular, to the high temperature treatment of sulfur-containing carbonaceous material. More particularly, one aspect of the invention relates to a method for continuously purifying and desulfurizing sulfur-containing carbonaceous material by maintaining the material in a fluidized bed and heating it to relatively high temperatures for a sufficient period of time to reduce the sulfur content of the material below about 0.5%. In another aspect of the invention, at least a portion of the material is transformed from a relatively amorphous molecular state to a more crystalline structure for the production of graphite.
It is well known in the art that carbonaceous material, such as calcined petroleum coke, can be almost completely desulfurized by subjecting it to relatively high temperatures, preferably in excess of 1700.degree. C. The graphitization of such material is time-temperature dependent, and can generally be accomplished by heating the material to even higher temperatures, preferably in excess of 2200.degree. C. Many existing systems, however, are incapable of achieving or maintaining the relatively high temperatures needed to advantageously and efficiently produce a high quality, uniformly purified product. Further, the desulfurization systems of the prior art have generally been incapable of economically reducing the sulfur content of the material below about 0.5%.
The prior art further shows numerous methods and apparatus attempting to uniformly heat various carbonaceous materials. Some of these methods and apparatus teach the use of a fluidizing stream to agitate the material during heating in a portion of a heating chamber known as a fluidizing zone. The combination of the fluidizing stream and the material agitated in the fluidizing zone is sometimes referred to herein as a fluidized bed. Heretofore it has been generally believed that treatment of material in a fluidized bed would be impractical or inefficient for particulate material of various sizes, particularly relatively large size particles, because of the difficulty of maintaining the large particles in a fluidized state even at high fluidizing gas flow rates.
Not only are some prior art material treatment systems limited by the desulfurization that can be achieved, or by the size of particulate material that can be economically fluidized, but they suffer from many other drawbacks and deficiencies as well. For example, many systems are incapable of treating material on a continuous basis, while others can produce commercial quantities of treated material only by utilizing a relatively large apparatus. Such apparatus, however, are generally too cumbersome or expensive to be practical.
It is thus a primary object of the invention to overcome these and other drawbacks in the prior art by providing an improved method and apparatus for treating sulfur-containing material such as particulate petroleum coke or other carbonaceous material.
It is another object of the invention to provide an improved material treatment system capable of achieving and maintaining the relatively high temperatures needed to advantageously and effeciently produce a high quality, uniformly desulfurized product having less than about 0.5% sulfur.
It is a further object of the invention to provide an improved material treatment system capable of agitating a variety of particle sizes, including relatively large sizes, in a fluidized bed with a minimal flow of fluidizing gas.
It is still another object of the invention to provide an improved material treatment system capable of continuously and economically producing commercial quantities of desulfurized material.
It is still another object of the invention to provide an improved material treatment system capable of economically transforming at least a portion of carbonaceous material from a relatively amorphous molecular state into a more crystalline graphitic structure.
Still another object of the invention is to provide an improved material treatment system capable of uniformly treating material of various sizes.
These and other objects of the invention are achieved by subjecting the sulfur-containing material of a fluidized bed to relatively high temperatures, generally not achieved in prior art systems. At these unusually high temperatures the fluidizing gas needed to maintain the material at a fluidized state is desirably, and unexpectedly, less than that which had been heretofore anticipated. Thus, where the prior art suggests that various size particles, particularly relatively large particles, could not be uniformly fluidized in a gas stream, this result can now be achieved. Moreover, through this technique, a sulfur-containing material can be continuously, economically, and uniformly treated so as to reduce the sulfur content below about 0.5%.